Difference between revisions of "BlackBerry : Develop Simple Apps"
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=== Bitmap Scaling ===
=== Bitmap Scaling ===
Revision as of 13:38, 24 February 2011
- Start and run the Eclipse for BlackBerry as installed in the previous lecture.
- Open the Subversion Perspective in Eclipse for BlackBerry.
- Check out the Simple Sample from BlackBerry Course Repository
- Run the sample and change it.
- Define the main steps involved in developing BlackBerry applications.
- Write a small tutorial (main steps) about using Eclipse to develop BlackBerry applications.
Start the lab activities in the order defined below:
Read Code from the BlackBerry Samples
Active Text Fields
The active text field sample application shows how a BlackBerry® device user can access customized items from the context menu when a pattern is recognized in an active text field. You can create active text fields by using theActiveAutoTextEditField class and ActiveRichTextField class.
When the BlackBerry device starts, the application, pattern, and associated menu items are registered with thePatternRepository. When text with the matching pattern is found in an active text field, the text is highlighted. When the user clicks highlighted text, the context menu is displayed with the menu items that are associated with the pattern.
In the sample application, when the user types a nine-digit number into an active text field, the user can click this number and a context menu with Status and Location options appears. When the user clicks one of the options, the application displays the requested information.
The bitmap scaling sample application demonstrates how to scale the size of a Bitmap image.
The sample application demostrates how to scale an original Bitmap image into new Bitmap objects, how to apply filters that help reduce the pixelated appearance of a scaled Bitmap image, and how to preserve the aspect ratio of the image.
The custom buttons sample application demonstrates how to extend the Field class to create a variety of different button UI components.
The sample application demonstrates how to create the following types of buttons:
- rectangle with a fixed width
- rectangle with a fixed width and a long text label
- rectangle with a full screen width
- rectangle with a color background
- rectangle with a .bmp image as the background
In addition to creating and displaying these custom buttons, the sample application also demonstrates how to attach listeners to these custom buttons. Listeners are components that execute code when an event occurs. In the sample application, when you click one of these buttons, a dialog box appears with text specifying which of the buttons you clicked.